New insights into the surface relaxation and oxidation of chalcopyrite exposed to O2 and H2O: A first-principles DFT study

Abstract In order to unravel the oxidation mechanism(s) of chalcopyrite (CuFeS 2 ) surfaces, the surface anisotropy of CuFeS 2 was investigated under both dry and aqueous atmospheres through a fundamental density functional theory (DFT) study. Results showed that the CuFeS 2 (112) surface was the preferred cleavage surface, rather than the commonly-assumed (001) surface. Iron oxides were formed when contacting with either molecular O 2 or dissociated O atoms, but sulfoxy species were only formed in the presence of dissociated O atoms, exposing Cu atoms on the S-terminated (001) and (112) surfaces. This indicates that strong oxidation conditions are beneficial to CuFeS 2 oxidation and the release of metals into solution. In addition, CuFeS 2 was preferentially oxidized by O 2 prior to the adsorption of H 2 O under an aqueous condition with both H 2 O and O 2 . The H 2 O adsorbed on the O-oxidized surface further promoted CuFeS 2 oxidation, resulting in the formation of a hydrophilic surface, rather than the naturally hydrophobic surface. This study has unveiled, for the first time, the mechanisms of the oxidation of the most stable and reactive CuFeS 2 (112) and (001) surfaces under both dry and aqueous environments at an atomic level, with potential applications in CuFeS 2 flotation and leaching processes.